Noob looking for help building latest for TP-Link TL-WR841N

looking to build custom firmware from latest OpenWR for TP-Link TL-WR841N.
Router currently has currently has 18.06.1.
Have gone through 'Beginners guide to building your own firmware' and that's working ok.
Looking for some advice on the Saving firmware space section.

Is there an easy way to modify build configuration variables to obtain the equivalent of the image builder command line ' `make image PROFILE="TP-LINK TL-WR841N/ND v8"
PACKAGES=“uhttpd uhttpd-mod-ubus libiwinfo-lua luci-base luci-app-firewall luci-mod-admin-full luci-theme-bootstrap zram-swap
-ppp -ppp-mod-pppoe -ip6tables -odhcp6c -kmod-ipv6 -kmod-ip6tables -odhcpd-ipv6only -opkg”'for my case?

(When) should I run make kernel_menuconfig to use those suggestions (e.g. make kernel_menuconfig CONFIG_TARGET=subtarget).

I really only want to use this device as a switch at this stage, but I'd like to keep the LuCi web admin interface, and I'd like to set up Extroot configuration (?), so I can use a usb on this device.

Happy to learn and sorry in advance for any annoying blunders / omissions.

Thanks for any help.